The invention relates to a method of incorporating chitosan reinforcement into an elastomer and elastomeric articles using Chitosan reinforcement.
Chitin is an abundant biopolymer with high potential reactivity and low density. It is obtained commercially as a shell fish by-product, and is potentially a very economical material.
The structure of chitin is similar to that of cellulose, which is commercially used as a reinforcing material (rayon) for rubber in Europe.
The crude material contains calcium carbonate, which is a known reinforcing material for the rubber industry.
Chitosan is a chemical derivative of chitin (a long unbranched polysaccharide (2-acetylamino-2-deoxy glucose)) and is readily prepared in the laboratory by deacetylation of the amino group (using a base or microbial fermentation) on the sugar ring to give a free amine. The reaction can be depicted as follows: ##STR1## This process makes the polymer more reactive and also yields a water soluble material. Chitosan is a linear polyelectrolyte with a high positive charge density at acidic pH. Chitosan is an excellent flocculent and adheres to negatively charged surfaces by way of the ammonium ion (--NH.sub.3 +). It also chelates a variety of metal ions (Fe, Cd, Hg, Pb, Cr, Ni). This biopolymer has good biological activity, and has been found useful for wound healing, in reduction of cholesterol levels in blood, and as an immune system stimulant. Chitosan has been used in cosmetics for hair treatment and in skin care. In the food industry, it has application as a fruit preservative as a spray, due to its excellent barrier properties.
In early experiments by the present inventors, Chitosan polymers, when blended with elastomers in the solid state, provided improvement in some low strain physical properties in cured rubber. The data showed a trend toward a decrease in physical properties with an increase in the particle size of the chitosan. However, commercial sources for grinding the material below 10 microns proved costly and were not feasible.
Japanese patent application 63-74073, filed Mar. 28, 1988, teaches the use of specialized equipment to pulverize chitin to obtain 0.5-40 micron particles for use in rubber reinforcement.
It is an object of the present invention to provide a unique, economical approach to obtain a reinforced elastomer having a tight range of smaller size chitosan particles by blending a chitosan solution with an elastomer latex. This technique eliminates the need for expensive equipment for reducing the chitosan particle size.
Other objects of the invention will be apparent from the following description and claims.